The findings of a new study suggest that side effects of Lotensin, Prinivil, Altace, Capoten, Monopril and other similar hypertension drugs, may increase the risk of lung cancer.

Canadian researchers warn that a class of blood pressure medications known as angiotensin converting enzyme (ACE) inhibitors may increase the risk of lung cancer by as much as 14%. While the increase is small, researchers warn that millions of people use the drugs, which means there could be a significant number of lung cancer cases linked to the drugs if the findings are confirmed.

The study was published in The BMJ on October 24, involving an observational population-based cohort study of nearly 1 million patients in the United Kingdom who were treated with antihypertensive drugs for the first time between January 1, 1995 and December 31, 2015. The participants were followed until December 31, 2016.

During the research, about 8,000 of the observed patients developed lung cancer. The researchers accounted for a number of potential causes, including age, gender, weight, smoking, drinking and a history of lung disease.

According to the findings, the overall use of ACE inhibitors was linked to a 14% increased risk of lung cancer, when compared to a competing class of drugs known as angiotensin receptor blockers, which includes drugs like Benicar and valsartan. In addition, researchers found that the longer ACE inhibitors were used, the higher the hazard ratio, with a 22% increased risk after five years, and a 31% increased risk after 10 years of use.

“In this population based cohort study, the use of ACEIs was associated with an increased risk of lung cancer,” the researchers concluded. “The association was particularly elevated among people using ACEIs for more than five years. Additional studies, with long term follow-up, are needed to investigate the effects of these drugs on incidence of lung cancer.”

Researchers noted that the overall risk was still low for patients, and that they had conducted an observational study that did not prove a causal link between drugs like Lotensin and Monopril, and lung cancer.